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  <div class="section" id="module-time">
<span id="time-time-access-and-conversions"></span><h1>16.3. <a class="reference internal" href="#module-time" title="time: Time access and conversions."><tt class="xref py py-mod docutils literal"><span class="pre">time</span></tt></a> &#8212; Time access and conversions<a class="headerlink" href="#module-time" title="Permalink to this headline">¶</a></h1>
<p>This module provides various time-related functions. For related
functionality, see also the <a class="reference internal" href="datetime.html#module-datetime" title="datetime: Basic date and time types."><tt class="xref py py-mod docutils literal"><span class="pre">datetime</span></tt></a> and <a class="reference internal" href="calendar.html#module-calendar" title="calendar: Functions for working with calendars, including some emulation of the Unix cal program."><tt class="xref py py-mod docutils literal"><span class="pre">calendar</span></tt></a> modules.</p>
<p>Although this module is always available,
not all functions are available on all platforms.  Most of the functions
defined in this module call platform C library functions with the same name.  It
may sometimes be helpful to consult the platform documentation, because the
semantics of these functions varies among platforms.</p>
<p>An explanation of some terminology and conventions is in order.</p>
<ul class="simple" id="index-0">
<li>The <em class="dfn">epoch</em> is the point where the time starts.  On January 1st of that
year, at 0 hours, the &#8220;time since the epoch&#8221; is zero.  For Unix, the epoch is
1970.  To find out what the epoch is, look at <tt class="docutils literal"><span class="pre">gmtime(0)</span></tt>.</li>
</ul>
<ul class="simple" id="index-1">
<li>The functions in this module may not handle dates and times before the epoch or
far in the future.  The cut-off point in the future is determined by the C
library; for 32-bit systems, it is typically in 2038.</li>
</ul>
<ul class="simple" id="time-y2kissues">
<span id="index-2"></span><li><strong>Year 2000 (Y2K) issues</strong>: Python depends on the platform&#8217;s C library, which
generally doesn&#8217;t have year 2000 issues, since all dates and times are
represented internally as seconds since the epoch.  Function <a class="reference internal" href="#time.strptime" title="time.strptime"><tt class="xref py py-func docutils literal"><span class="pre">strptime()</span></tt></a>
can parse 2-digit years when given <tt class="docutils literal"><span class="pre">%y</span></tt> format code.  When 2-digit years are
parsed, they are converted according to the POSIX and ISO C standards: values
69&#8211;99 are mapped to 1969&#8211;1999, and values 0&#8211;68 are mapped to 2000&#8211;2068.</li>
</ul>
<ul class="simple" id="index-3">
<li>UTC is Coordinated Universal Time (formerly known as Greenwich Mean Time, or
GMT).  The acronym UTC is not a mistake but a compromise between English and
French.</li>
</ul>
<ul id="index-4">
<li><p class="first">DST is Daylight Saving Time, an adjustment of the timezone by (usually) one
hour during part of the year.  DST rules are magic (determined by local law) and
can change from year to year.  The C library has a table containing the local
rules (often it is read from a system file for flexibility) and is the only
source of True Wisdom in this respect.</p>
</li>
<li><p class="first">The precision of the various real-time functions may be less than suggested by
the units in which their value or argument is expressed. E.g. on most Unix
systems, the clock &#8220;ticks&#8221; only 50 or 100 times a second.</p>
</li>
<li><p class="first">On the other hand, the precision of <a class="reference internal" href="#time.time" title="time.time"><tt class="xref py py-func docutils literal"><span class="pre">time()</span></tt></a> and <a class="reference internal" href="#time.sleep" title="time.sleep"><tt class="xref py py-func docutils literal"><span class="pre">sleep()</span></tt></a> is better
than their Unix equivalents: times are expressed as floating point numbers,
<a class="reference internal" href="#time.time" title="time.time"><tt class="xref py py-func docutils literal"><span class="pre">time()</span></tt></a> returns the most accurate time available (using Unix
<tt class="xref c c-func docutils literal"><span class="pre">gettimeofday()</span></tt> where available), and <a class="reference internal" href="#time.sleep" title="time.sleep"><tt class="xref py py-func docutils literal"><span class="pre">sleep()</span></tt></a> will accept a time
with a nonzero fraction (Unix <tt class="xref c c-func docutils literal"><span class="pre">select()</span></tt> is used to implement this, where
available).</p>
</li>
<li><p class="first">The time value as returned by <a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a>, <a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a>, and
<a class="reference internal" href="#time.strptime" title="time.strptime"><tt class="xref py py-func docutils literal"><span class="pre">strptime()</span></tt></a>, and accepted by <a class="reference internal" href="#time.asctime" title="time.asctime"><tt class="xref py py-func docutils literal"><span class="pre">asctime()</span></tt></a>, <a class="reference internal" href="#time.mktime" title="time.mktime"><tt class="xref py py-func docutils literal"><span class="pre">mktime()</span></tt></a> and
<a class="reference internal" href="#time.strftime" title="time.strftime"><tt class="xref py py-func docutils literal"><span class="pre">strftime()</span></tt></a>, is a sequence of 9 integers.  The return values of
<a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a>, <a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a>, and <a class="reference internal" href="#time.strptime" title="time.strptime"><tt class="xref py py-func docutils literal"><span class="pre">strptime()</span></tt></a> also offer attribute
names for individual fields.</p>
<p>See <a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> for a description of these objects.</p>
<div class="versionchanged">
<p><span class="versionmodified">Changed in version 3.3: </span>The <a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> type was extended to provide the <tt class="xref py py-attr docutils literal"><span class="pre">tm_gmtoff</span></tt>
and <tt class="xref py py-attr docutils literal"><span class="pre">tm_zone</span></tt> attributes when platform supports corresponding
<tt class="docutils literal"><span class="pre">struct</span> <span class="pre">tm</span></tt> members.</p>
</div>
</li>
<li><p class="first">Use the following functions to convert between time representations:</p>
<table border="1" class="docutils">
<colgroup>
<col width="33%" />
<col width="33%" />
<col width="33%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">From</th>
<th class="head">To</th>
<th class="head">Use</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>seconds since the epoch</td>
<td><a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> in
UTC</td>
<td><a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a></td>
</tr>
<tr class="row-odd"><td>seconds since the epoch</td>
<td><a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> in
local time</td>
<td><a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a></td>
</tr>
<tr class="row-even"><td><a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> in
UTC</td>
<td>seconds since the epoch</td>
<td><a class="reference internal" href="calendar.html#calendar.timegm" title="calendar.timegm"><tt class="xref py py-func docutils literal"><span class="pre">calendar.timegm()</span></tt></a></td>
</tr>
<tr class="row-odd"><td><a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> in
local time</td>
<td>seconds since the epoch</td>
<td><a class="reference internal" href="#time.mktime" title="time.mktime"><tt class="xref py py-func docutils literal"><span class="pre">mktime()</span></tt></a></td>
</tr>
</tbody>
</table>
</li>
</ul>
<p>The module defines the following functions and data items:</p>
<dl class="data">
<dt id="time.altzone">
<tt class="descclassname">time.</tt><tt class="descname">altzone</tt><a class="headerlink" href="#time.altzone" title="Permalink to this definition">¶</a></dt>
<dd><p>The offset of the local DST timezone, in seconds west of UTC, if one is defined.
This is negative if the local DST timezone is east of UTC (as in Western Europe,
including the UK).  Only use this if <tt class="docutils literal"><span class="pre">daylight</span></tt> is nonzero.</p>
</dd></dl>

<dl class="function">
<dt id="time.asctime">
<tt class="descclassname">time.</tt><tt class="descname">asctime</tt><big>(</big><span class="optional">[</span><em>t</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#time.asctime" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert a tuple or <a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> representing a time as returned by
<a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a> or <a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a> to a string of the following
form: <tt class="docutils literal"><span class="pre">'Sun</span> <span class="pre">Jun</span> <span class="pre">20</span> <span class="pre">23:21:05</span> <span class="pre">1993'</span></tt>.  If <em>t</em> is not provided, the current time
as returned by <a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a> is used. Locale information is not used by
<a class="reference internal" href="#time.asctime" title="time.asctime"><tt class="xref py py-func docutils literal"><span class="pre">asctime()</span></tt></a>.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Unlike the C function of the same name, <a class="reference internal" href="#time.asctime" title="time.asctime"><tt class="xref py py-func docutils literal"><span class="pre">asctime()</span></tt></a> does not add a
trailing newline.</p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.clock">
<tt class="descclassname">time.</tt><tt class="descname">clock</tt><big>(</big><big>)</big><a class="headerlink" href="#time.clock" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-5">On Unix, return the current processor time as a floating point number expressed
in seconds.  The precision, and in fact the very definition of the meaning of
&#8220;processor time&#8221;, depends on that of the C function of the same name.</p>
<p>On Windows, this function returns wall-clock seconds elapsed since the first
call to this function, as a floating point number, based on the Win32 function
<tt class="xref c c-func docutils literal"><span class="pre">QueryPerformanceCounter()</span></tt>. The resolution is typically better than one
microsecond.</p>
<div class="deprecated">
<p><span class="versionmodified">Deprecated since version 3.3: </span>The behaviour of this function depends on the platform: use
<a class="reference internal" href="#time.perf_counter" title="time.perf_counter"><tt class="xref py py-func docutils literal"><span class="pre">perf_counter()</span></tt></a> or <a class="reference internal" href="#time.process_time" title="time.process_time"><tt class="xref py py-func docutils literal"><span class="pre">process_time()</span></tt></a> instead, depending on your
requirements, to have a well defined behaviour.</p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.clock_getres">
<tt class="descclassname">time.</tt><tt class="descname">clock_getres</tt><big>(</big><em>clk_id</em><big>)</big><a class="headerlink" href="#time.clock_getres" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the resolution (precision) of the specified clock <em>clk_id</em>.</p>
<p>Availability: Unix.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.clock_gettime">
<tt class="descclassname">time.</tt><tt class="descname">clock_gettime</tt><big>(</big><em>clk_id</em><big>)</big><a class="headerlink" href="#time.clock_gettime" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the time of the specified clock <em>clk_id</em>.</p>
<p>Availability: Unix.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.clock_settime">
<tt class="descclassname">time.</tt><tt class="descname">clock_settime</tt><big>(</big><em>clk_id</em>, <em>time</em><big>)</big><a class="headerlink" href="#time.clock_settime" title="Permalink to this definition">¶</a></dt>
<dd><p>Set the time of the specified clock <em>clk_id</em>.</p>
<p>Availability: Unix.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="data">
<dt id="time.CLOCK_HIGHRES">
<tt class="descclassname">time.</tt><tt class="descname">CLOCK_HIGHRES</tt><a class="headerlink" href="#time.CLOCK_HIGHRES" title="Permalink to this definition">¶</a></dt>
<dd><p>The Solaris OS has a CLOCK_HIGHRES timer that attempts to use an optimal
hardware source, and may give close to nanosecond resolution.  CLOCK_HIGHRES
is the nonadjustable, high-resolution clock.</p>
<p>Availability: Solaris.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="data">
<dt id="time.CLOCK_MONOTONIC">
<tt class="descclassname">time.</tt><tt class="descname">CLOCK_MONOTONIC</tt><a class="headerlink" href="#time.CLOCK_MONOTONIC" title="Permalink to this definition">¶</a></dt>
<dd><p>Clock that cannot be set and represents monotonic time since some unspecified
starting point.</p>
<p>Availability: Unix.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="data">
<dt id="time.CLOCK_MONOTONIC_RAW">
<tt class="descclassname">time.</tt><tt class="descname">CLOCK_MONOTONIC_RAW</tt><a class="headerlink" href="#time.CLOCK_MONOTONIC_RAW" title="Permalink to this definition">¶</a></dt>
<dd><p>Similar to <a class="reference internal" href="#time.CLOCK_MONOTONIC" title="time.CLOCK_MONOTONIC"><tt class="xref py py-data docutils literal"><span class="pre">CLOCK_MONOTONIC</span></tt></a>, but provides access to a raw
hardware-based time that is not subject to NTP adjustments.</p>
<p>Availability: Linux 2.6.28 or later.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="data">
<dt id="time.CLOCK_PROCESS_CPUTIME_ID">
<tt class="descclassname">time.</tt><tt class="descname">CLOCK_PROCESS_CPUTIME_ID</tt><a class="headerlink" href="#time.CLOCK_PROCESS_CPUTIME_ID" title="Permalink to this definition">¶</a></dt>
<dd><p>High-resolution per-process timer from the CPU.</p>
<p>Availability: Unix.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="data">
<dt id="time.CLOCK_REALTIME">
<tt class="descclassname">time.</tt><tt class="descname">CLOCK_REALTIME</tt><a class="headerlink" href="#time.CLOCK_REALTIME" title="Permalink to this definition">¶</a></dt>
<dd><p>System-wide real-time clock.  Setting this clock requires appropriate
privileges.</p>
<p>Availability: Unix.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="data">
<dt id="time.CLOCK_THREAD_CPUTIME_ID">
<tt class="descclassname">time.</tt><tt class="descname">CLOCK_THREAD_CPUTIME_ID</tt><a class="headerlink" href="#time.CLOCK_THREAD_CPUTIME_ID" title="Permalink to this definition">¶</a></dt>
<dd><p>Thread-specific CPU-time clock.</p>
<p>Availability: Unix.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.ctime">
<tt class="descclassname">time.</tt><tt class="descname">ctime</tt><big>(</big><span class="optional">[</span><em>secs</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#time.ctime" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert a time expressed in seconds since the epoch to a string representing
local time. If <em>secs</em> is not provided or <a class="reference internal" href="constants.html#None" title="None"><tt class="xref py py-const docutils literal"><span class="pre">None</span></tt></a>, the current time as
returned by <a class="reference internal" href="#time.time" title="time.time"><tt class="xref py py-func docutils literal"><span class="pre">time()</span></tt></a> is used.  <tt class="docutils literal"><span class="pre">ctime(secs)</span></tt> is equivalent to
<tt class="docutils literal"><span class="pre">asctime(localtime(secs))</span></tt>. Locale information is not used by <a class="reference internal" href="#time.ctime" title="time.ctime"><tt class="xref py py-func docutils literal"><span class="pre">ctime()</span></tt></a>.</p>
</dd></dl>

<dl class="data">
<dt id="time.daylight">
<tt class="descclassname">time.</tt><tt class="descname">daylight</tt><a class="headerlink" href="#time.daylight" title="Permalink to this definition">¶</a></dt>
<dd><p>Nonzero if a DST timezone is defined.</p>
</dd></dl>

<dl class="function">
<dt id="time.get_clock_info">
<tt class="descclassname">time.</tt><tt class="descname">get_clock_info</tt><big>(</big><em>name</em><big>)</big><a class="headerlink" href="#time.get_clock_info" title="Permalink to this definition">¶</a></dt>
<dd><p>Get information on the specified clock as a namespace object.
Supported clock names and the corresponding functions to read their value
are:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">'clock'</span></tt>: <a class="reference internal" href="#time.clock" title="time.clock"><tt class="xref py py-func docutils literal"><span class="pre">time.clock()</span></tt></a></li>
<li><tt class="docutils literal"><span class="pre">'monotonic'</span></tt>: <a class="reference internal" href="#time.monotonic" title="time.monotonic"><tt class="xref py py-func docutils literal"><span class="pre">time.monotonic()</span></tt></a></li>
<li><tt class="docutils literal"><span class="pre">'perf_counter'</span></tt>: <a class="reference internal" href="#time.perf_counter" title="time.perf_counter"><tt class="xref py py-func docutils literal"><span class="pre">time.perf_counter()</span></tt></a></li>
<li><tt class="docutils literal"><span class="pre">'process_time'</span></tt>: <a class="reference internal" href="#time.process_time" title="time.process_time"><tt class="xref py py-func docutils literal"><span class="pre">time.process_time()</span></tt></a></li>
<li><tt class="docutils literal"><span class="pre">'time'</span></tt>: <a class="reference internal" href="#time.time" title="time.time"><tt class="xref py py-func docutils literal"><span class="pre">time.time()</span></tt></a></li>
</ul>
<p>The result has the following attributes:</p>
<ul class="simple">
<li><em>adjustable</em>: <tt class="docutils literal"><span class="pre">True</span></tt> if the clock can be changed automatically (e.g. by
a NTP daemon) or manually by the system administrator, <tt class="docutils literal"><span class="pre">False</span></tt> otherwise</li>
<li><em>implementation</em>: The name of the underlying C function used to get
the clock value</li>
<li><em>monotonic</em>: <tt class="docutils literal"><span class="pre">True</span></tt> if the clock cannot go backward,
<tt class="docutils literal"><span class="pre">False</span></tt> otherwise</li>
<li><em>resolution</em>: The resolution of the clock in seconds (<a class="reference internal" href="functions.html#float" title="float"><tt class="xref py py-class docutils literal"><span class="pre">float</span></tt></a>)</li>
</ul>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.gmtime">
<tt class="descclassname">time.</tt><tt class="descname">gmtime</tt><big>(</big><span class="optional">[</span><em>secs</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#time.gmtime" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert a time expressed in seconds since the epoch to a <a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> in
UTC in which the dst flag is always zero.  If <em>secs</em> is not provided or
<a class="reference internal" href="constants.html#None" title="None"><tt class="xref py py-const docutils literal"><span class="pre">None</span></tt></a>, the current time as returned by <a class="reference internal" href="#time.time" title="time.time"><tt class="xref py py-func docutils literal"><span class="pre">time()</span></tt></a> is used.  Fractions
of a second are ignored.  See above for a description of the
<a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> object. See <a class="reference internal" href="calendar.html#calendar.timegm" title="calendar.timegm"><tt class="xref py py-func docutils literal"><span class="pre">calendar.timegm()</span></tt></a> for the inverse of this
function.</p>
</dd></dl>

<dl class="function">
<dt id="time.localtime">
<tt class="descclassname">time.</tt><tt class="descname">localtime</tt><big>(</big><span class="optional">[</span><em>secs</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#time.localtime" title="Permalink to this definition">¶</a></dt>
<dd><p>Like <a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a> but converts to local time.  If <em>secs</em> is not provided or
<a class="reference internal" href="constants.html#None" title="None"><tt class="xref py py-const docutils literal"><span class="pre">None</span></tt></a>, the current time as returned by <a class="reference internal" href="#time.time" title="time.time"><tt class="xref py py-func docutils literal"><span class="pre">time()</span></tt></a> is used.  The dst
flag is set to <tt class="docutils literal"><span class="pre">1</span></tt> when DST applies to the given time.</p>
</dd></dl>

<dl class="function">
<dt id="time.mktime">
<tt class="descclassname">time.</tt><tt class="descname">mktime</tt><big>(</big><em>t</em><big>)</big><a class="headerlink" href="#time.mktime" title="Permalink to this definition">¶</a></dt>
<dd><p>This is the inverse function of <a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a>.  Its argument is the
<a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> or full 9-tuple (since the dst flag is needed; use <tt class="docutils literal"><span class="pre">-1</span></tt>
as the dst flag if it is unknown) which expresses the time in <em>local</em> time, not
UTC.  It returns a floating point number, for compatibility with <a class="reference internal" href="#time.time" title="time.time"><tt class="xref py py-func docutils literal"><span class="pre">time()</span></tt></a>.
If the input value cannot be represented as a valid time, either
<a class="reference internal" href="exceptions.html#OverflowError" title="OverflowError"><tt class="xref py py-exc docutils literal"><span class="pre">OverflowError</span></tt></a> or <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><tt class="xref py py-exc docutils literal"><span class="pre">ValueError</span></tt></a> will be raised (which depends on
whether the invalid value is caught by Python or the underlying C libraries).
The earliest date for which it can generate a time is platform-dependent.</p>
</dd></dl>

<dl class="function">
<dt id="time.monotonic">
<tt class="descclassname">time.</tt><tt class="descname">monotonic</tt><big>(</big><big>)</big><a class="headerlink" href="#time.monotonic" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the value (in fractional seconds) of a monotonic clock, i.e. a clock
that cannot go backwards.  The clock is not affected by system clock updates.
The reference point of the returned value is undefined, so that only the
difference between the results of consecutive calls is valid.</p>
<p>On Windows versions older than Vista, <a class="reference internal" href="#time.monotonic" title="time.monotonic"><tt class="xref py py-func docutils literal"><span class="pre">monotonic()</span></tt></a> detects
<tt class="xref c c-func docutils literal"><span class="pre">GetTickCount()</span></tt> integer overflow (32 bits, roll-over after 49.7 days).
It increases an internal epoch (reference time) by 2<sup>32</sup> each time
that an overflow is detected.  The epoch is stored in the process-local state
and so the value of <a class="reference internal" href="#time.monotonic" title="time.monotonic"><tt class="xref py py-func docutils literal"><span class="pre">monotonic()</span></tt></a> may be different in two Python
processes running for more than 49 days. On more recent versions of Windows
and on other operating systems, <a class="reference internal" href="#time.monotonic" title="time.monotonic"><tt class="xref py py-func docutils literal"><span class="pre">monotonic()</span></tt></a> is system-wide.</p>
<p>Availability: Windows, Mac OS X, Linux, FreeBSD, OpenBSD, Solaris.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.perf_counter">
<tt class="descclassname">time.</tt><tt class="descname">perf_counter</tt><big>(</big><big>)</big><a class="headerlink" href="#time.perf_counter" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the value (in fractional seconds) of a performance counter, i.e. a
clock with the highest available resolution to measure a short duration.  It
does include time elapsed during sleep and is system-wide.  The reference
point of the returned value is undefined, so that only the difference between
the results of consecutive calls is valid.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.process_time">
<tt class="descclassname">time.</tt><tt class="descname">process_time</tt><big>(</big><big>)</big><a class="headerlink" href="#time.process_time" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the value (in fractional seconds) of the sum of the system and user
CPU time of the current process.  It does not include time elapsed during
sleep.  It is process-wide by definition.  The reference point of the
returned value is undefined, so that only the difference between the results
of consecutive calls is valid.</p>
<div class="versionadded">
<p><span class="versionmodified">New in version 3.3.</span></p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.sleep">
<tt class="descclassname">time.</tt><tt class="descname">sleep</tt><big>(</big><em>secs</em><big>)</big><a class="headerlink" href="#time.sleep" title="Permalink to this definition">¶</a></dt>
<dd><p>Suspend execution of the calling thread for the given number of seconds.
The argument may be a floating point number to indicate a more precise sleep
time. The actual suspension time may be less than that requested because any
caught signal will terminate the <a class="reference internal" href="#time.sleep" title="time.sleep"><tt class="xref py py-func docutils literal"><span class="pre">sleep()</span></tt></a> following execution of that
signal&#8217;s catching routine.  Also, the suspension time may be longer than
requested by an arbitrary amount because of the scheduling of other activity
in the system.</p>
</dd></dl>

<dl class="function">
<dt id="time.strftime">
<tt class="descclassname">time.</tt><tt class="descname">strftime</tt><big>(</big><em>format</em><span class="optional">[</span>, <em>t</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#time.strftime" title="Permalink to this definition">¶</a></dt>
<dd><p>Convert a tuple or <a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> representing a time as returned by
<a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a> or <a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a> to a string as specified by the <em>format</em>
argument.  If <em>t</em> is not provided, the current time as returned by
<a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a> is used.  <em>format</em> must be a string.  <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><tt class="xref py py-exc docutils literal"><span class="pre">ValueError</span></tt></a> is
raised if any field in <em>t</em> is outside of the allowed range.</p>
<p>0 is a legal argument for any position in the time tuple; if it is normally
illegal the value is forced to a correct one.</p>
<p>The following directives can be embedded in the <em>format</em> string. They are shown
without the optional field width and precision specification, and are replaced
by the indicated characters in the <a class="reference internal" href="#time.strftime" title="time.strftime"><tt class="xref py py-func docutils literal"><span class="pre">strftime()</span></tt></a> result:</p>
<table border="1" class="docutils">
<colgroup>
<col width="17%" />
<col width="73%" />
<col width="11%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Directive</th>
<th class="head">Meaning</th>
<th class="head">Notes</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%a</span></tt></td>
<td>Locale&#8217;s abbreviated weekday name.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%A</span></tt></td>
<td>Locale&#8217;s full weekday name.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%b</span></tt></td>
<td>Locale&#8217;s abbreviated month name.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%B</span></tt></td>
<td>Locale&#8217;s full month name.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%c</span></tt></td>
<td>Locale&#8217;s appropriate date and time
representation.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%d</span></tt></td>
<td>Day of the month as a decimal number [01,31].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%H</span></tt></td>
<td>Hour (24-hour clock) as a decimal number
[00,23].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%I</span></tt></td>
<td>Hour (12-hour clock) as a decimal number
[01,12].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%j</span></tt></td>
<td>Day of the year as a decimal number [001,366].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%m</span></tt></td>
<td>Month as a decimal number [01,12].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%M</span></tt></td>
<td>Minute as a decimal number [00,59].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%p</span></tt></td>
<td>Locale&#8217;s equivalent of either AM or PM.</td>
<td>(1)</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%S</span></tt></td>
<td>Second as a decimal number [00,61].</td>
<td>(2)</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%U</span></tt></td>
<td>Week number of the year (Sunday as the first
day of the week) as a decimal number [00,53].
All days in a new year preceding the first
Sunday are considered to be in week 0.</td>
<td>(3)</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%w</span></tt></td>
<td>Weekday as a decimal number [0(Sunday),6].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%W</span></tt></td>
<td>Week number of the year (Monday as the first
day of the week) as a decimal number [00,53].
All days in a new year preceding the first
Monday are considered to be in week 0.</td>
<td>(3)</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%x</span></tt></td>
<td>Locale&#8217;s appropriate date representation.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%X</span></tt></td>
<td>Locale&#8217;s appropriate time representation.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%y</span></tt></td>
<td>Year without century as a decimal number
[00,99].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%Y</span></tt></td>
<td>Year with century as a decimal number.</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%z</span></tt></td>
<td>Time zone offset indicating a positive or
negative time difference from UTC/GMT of the
form +HHMM or -HHMM, where H represents decimal
hour digits and M represents decimal minute
digits [-23:59, +23:59].</td>
<td>&nbsp;</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%Z</span></tt></td>
<td>Time zone name (no characters if no time zone
exists).</td>
<td>&nbsp;</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%%</span></tt></td>
<td>A literal <tt class="docutils literal"><span class="pre">'%'</span></tt> character.</td>
<td>&nbsp;</td>
</tr>
</tbody>
</table>
<p>Notes:</p>
<ol class="arabic simple">
<li>When used with the <a class="reference internal" href="#time.strptime" title="time.strptime"><tt class="xref py py-func docutils literal"><span class="pre">strptime()</span></tt></a> function, the <tt class="docutils literal"><span class="pre">%p</span></tt> directive only affects
the output hour field if the <tt class="docutils literal"><span class="pre">%I</span></tt> directive is used to parse the hour.</li>
<li>The range really is <tt class="docutils literal"><span class="pre">0</span></tt> to <tt class="docutils literal"><span class="pre">61</span></tt>; value <tt class="docutils literal"><span class="pre">60</span></tt> is valid in
timestamps representing leap seconds and value <tt class="docutils literal"><span class="pre">61</span></tt> is supported
for historical reasons.</li>
<li>When used with the <a class="reference internal" href="#time.strptime" title="time.strptime"><tt class="xref py py-func docutils literal"><span class="pre">strptime()</span></tt></a> function, <tt class="docutils literal"><span class="pre">%U</span></tt> and <tt class="docutils literal"><span class="pre">%W</span></tt> are only used in
calculations when the day of the week and the year are specified.</li>
</ol>
<p>Here is an example, a format for dates compatible with that specified  in the
<span class="target" id="index-6"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a> Internet email standard.  <a class="footnote-reference" href="#id2" id="id1">[1]</a></p>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">time</span> <span class="k">import</span> <span class="n">gmtime</span><span class="p">,</span> <span class="n">strftime</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">strftime</span><span class="p">(</span><span class="s">&quot;%a, %d %b %Y %H:%M:%S +0000&quot;</span><span class="p">,</span> <span class="n">gmtime</span><span class="p">())</span>
<span class="go">&#39;Thu, 28 Jun 2001 14:17:15 +0000&#39;</span>
</pre></div>
</div>
<p>Additional directives may be supported on certain platforms, but only the
ones listed here have a meaning standardized by ANSI C.  To see the full set
of format codes supported on your platform, consult the <em class="manpage">strftime(3)</em>
documentation.</p>
<p>On some platforms, an optional field width and precision specification can
immediately follow the initial <tt class="docutils literal"><span class="pre">'%'</span></tt> of a directive in the following order;
this is also not portable. The field width is normally 2 except for <tt class="docutils literal"><span class="pre">%j</span></tt> where
it is 3.</p>
</dd></dl>

<dl class="function">
<dt id="time.strptime">
<tt class="descclassname">time.</tt><tt class="descname">strptime</tt><big>(</big><em>string</em><span class="optional">[</span>, <em>format</em><span class="optional">]</span><big>)</big><a class="headerlink" href="#time.strptime" title="Permalink to this definition">¶</a></dt>
<dd><p>Parse a string representing a time according to a format.  The return value
is a <a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a> as returned by <a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a> or
<a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a>.</p>
<p>The <em>format</em> parameter uses the same directives as those used by
<a class="reference internal" href="#time.strftime" title="time.strftime"><tt class="xref py py-func docutils literal"><span class="pre">strftime()</span></tt></a>; it defaults to <tt class="docutils literal"><span class="pre">&quot;%a</span> <span class="pre">%b</span> <span class="pre">%d</span> <span class="pre">%H:%M:%S</span> <span class="pre">%Y&quot;</span></tt> which matches the
formatting returned by <a class="reference internal" href="#time.ctime" title="time.ctime"><tt class="xref py py-func docutils literal"><span class="pre">ctime()</span></tt></a>. If <em>string</em> cannot be parsed according
to <em>format</em>, or if it has excess data after parsing, <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><tt class="xref py py-exc docutils literal"><span class="pre">ValueError</span></tt></a> is
raised. The default values used to fill in any missing data when more
accurate values cannot be inferred are <tt class="docutils literal"><span class="pre">(1900,</span> <span class="pre">1,</span> <span class="pre">1,</span> <span class="pre">0,</span> <span class="pre">0,</span> <span class="pre">0,</span> <span class="pre">0,</span> <span class="pre">1,</span> <span class="pre">-1)</span></tt>.
Both <em>string</em> and <em>format</em> must be strings.</p>
<p>For example:</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">time</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">strptime</span><span class="p">(</span><span class="s">&quot;30 Nov 00&quot;</span><span class="p">,</span> <span class="s">&quot;%d %b %y&quot;</span><span class="p">)</span>   
<span class="go">time.struct_time(tm_year=2000, tm_mon=11, tm_mday=30, tm_hour=0, tm_min=0,</span>
<span class="go">                 tm_sec=0, tm_wday=3, tm_yday=335, tm_isdst=-1)</span>
</pre></div>
</div>
<p>Support for the <tt class="docutils literal"><span class="pre">%Z</span></tt> directive is based on the values contained in <tt class="docutils literal"><span class="pre">tzname</span></tt>
and whether <tt class="docutils literal"><span class="pre">daylight</span></tt> is true.  Because of this, it is platform-specific
except for recognizing UTC and GMT which are always known (and are considered to
be non-daylight savings timezones).</p>
<p>Only the directives specified in the documentation are supported.  Because
<tt class="docutils literal"><span class="pre">strftime()</span></tt> is implemented per platform it can sometimes offer more
directives than those listed.  But <tt class="docutils literal"><span class="pre">strptime()</span></tt> is independent of any platform
and thus does not necessarily support all directives available that are not
documented as supported.</p>
</dd></dl>

<dl class="class">
<dt id="time.struct_time">
<em class="property">class </em><tt class="descclassname">time.</tt><tt class="descname">struct_time</tt><a class="headerlink" href="#time.struct_time" title="Permalink to this definition">¶</a></dt>
<dd><blockquote>
<div><p>The type of the time value sequence returned by <a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a>,
<a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a>, and <a class="reference internal" href="#time.strptime" title="time.strptime"><tt class="xref py py-func docutils literal"><span class="pre">strptime()</span></tt></a>.  It is an object with a <a class="reference internal" href="../glossary.html#term-named-tuple"><em class="xref std std-term">named
tuple</em></a> interface: values can be accessed by index and by attribute name.  The
following values are present:</p>
<table border="1" class="docutils">
<colgroup>
<col width="12%" />
<col width="32%" />
<col width="56%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Index</th>
<th class="head">Attribute</th>
<th class="head">Values</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>0</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_year</span></tt></td>
<td>(for example, 1993)</td>
</tr>
<tr class="row-odd"><td>1</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_mon</span></tt></td>
<td>range [1, 12]</td>
</tr>
<tr class="row-even"><td>2</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_mday</span></tt></td>
<td>range [1, 31]</td>
</tr>
<tr class="row-odd"><td>3</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_hour</span></tt></td>
<td>range [0, 23]</td>
</tr>
<tr class="row-even"><td>4</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_min</span></tt></td>
<td>range [0, 59]</td>
</tr>
<tr class="row-odd"><td>5</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_sec</span></tt></td>
<td>range [0, 61]; see <strong>(2)</strong> in
<a class="reference internal" href="#time.strftime" title="time.strftime"><tt class="xref py py-func docutils literal"><span class="pre">strftime()</span></tt></a> description</td>
</tr>
<tr class="row-even"><td>6</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_wday</span></tt></td>
<td>range [0, 6], Monday is 0</td>
</tr>
<tr class="row-odd"><td>7</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_yday</span></tt></td>
<td>range [1, 366]</td>
</tr>
<tr class="row-even"><td>8</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_isdst</span></tt></td>
<td>0, 1 or -1; see below</td>
</tr>
<tr class="row-odd"><td>N/A</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_zone</span></tt></td>
<td>abbreviation of timezone name</td>
</tr>
<tr class="row-even"><td>N/A</td>
<td><tt class="xref py py-attr docutils literal"><span class="pre">tm_gmtoff</span></tt></td>
<td>offset east of UTC in seconds</td>
</tr>
</tbody>
</table>
<p>Note that unlike the C structure, the month value is a range of [1, 12], not
[0, 11].  A <tt class="docutils literal"><span class="pre">-1</span></tt> argument as the daylight
savings flag, passed to <a class="reference internal" href="#time.mktime" title="time.mktime"><tt class="xref py py-func docutils literal"><span class="pre">mktime()</span></tt></a> will usually result in the correct
daylight savings state to be filled in.</p>
<p>When a tuple with an incorrect length is passed to a function expecting a
<a class="reference internal" href="#time.struct_time" title="time.struct_time"><tt class="xref py py-class docutils literal"><span class="pre">struct_time</span></tt></a>, or having elements of the wrong type, a
<a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><tt class="xref py py-exc docutils literal"><span class="pre">TypeError</span></tt></a> is raised.</p>
</div></blockquote>
<div class="versionchanged">
<p><span class="versionmodified">Changed in version 3.3: </span><tt class="xref py py-attr docutils literal"><span class="pre">tm_gmtoff</span></tt> and <tt class="xref py py-attr docutils literal"><span class="pre">tm_zone</span></tt> attributes are available on platforms
with C library supporting the corresponding fields in <tt class="docutils literal"><span class="pre">struct</span> <span class="pre">tm</span></tt>.</p>
</div>
</dd></dl>

<dl class="function">
<dt id="time.time">
<tt class="descclassname">time.</tt><tt class="descname">time</tt><big>(</big><big>)</big><a class="headerlink" href="#time.time" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the time in seconds since the epoch as a floating point number.
Note that even though the time is always returned as a floating point
number, not all systems provide time with a better precision than 1 second.
While this function normally returns non-decreasing values, it can return a
lower value than a previous call if the system clock has been set back between
the two calls.</p>
</dd></dl>

<dl class="data">
<dt id="time.timezone">
<tt class="descclassname">time.</tt><tt class="descname">timezone</tt><a class="headerlink" href="#time.timezone" title="Permalink to this definition">¶</a></dt>
<dd><p>The offset of the local (non-DST) timezone, in seconds west of UTC (negative in
most of Western Europe, positive in the US, zero in the UK).</p>
</dd></dl>

<dl class="data">
<dt id="time.tzname">
<tt class="descclassname">time.</tt><tt class="descname">tzname</tt><a class="headerlink" href="#time.tzname" title="Permalink to this definition">¶</a></dt>
<dd><p>A tuple of two strings: the first is the name of the local non-DST timezone, the
second is the name of the local DST timezone.  If no DST timezone is defined,
the second string should not be used.</p>
</dd></dl>

<dl class="function">
<dt id="time.tzset">
<tt class="descclassname">time.</tt><tt class="descname">tzset</tt><big>(</big><big>)</big><a class="headerlink" href="#time.tzset" title="Permalink to this definition">¶</a></dt>
<dd><p>Resets the time conversion rules used by the library routines. The environment
variable <span class="target" id="index-7"></span><tt class="xref std std-envvar docutils literal"><span class="pre">TZ</span></tt> specifies how this is done.</p>
<p>Availability: Unix.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>Although in many cases, changing the <span class="target" id="index-8"></span><tt class="xref std std-envvar docutils literal"><span class="pre">TZ</span></tt> environment variable may
affect the output of functions like <a class="reference internal" href="#time.localtime" title="time.localtime"><tt class="xref py py-func docutils literal"><span class="pre">localtime()</span></tt></a> without calling
<a class="reference internal" href="#time.tzset" title="time.tzset"><tt class="xref py py-func docutils literal"><span class="pre">tzset()</span></tt></a>, this behavior should not be relied on.</p>
<p class="last">The <span class="target" id="index-9"></span><tt class="xref std std-envvar docutils literal"><span class="pre">TZ</span></tt> environment variable should contain no whitespace.</p>
</div>
<p>The standard format of the <span class="target" id="index-10"></span><tt class="xref std std-envvar docutils literal"><span class="pre">TZ</span></tt> environment variable is (whitespace
added for clarity):</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="n">std</span> <span class="n">offset</span> <span class="p">[</span><span class="n">dst</span> <span class="p">[</span><span class="n">offset</span> <span class="p">[,</span><span class="n">start</span><span class="p">[</span><span class="o">/</span><span class="n">time</span><span class="p">],</span> <span class="n">end</span><span class="p">[</span><span class="o">/</span><span class="n">time</span><span class="p">]]]]</span>
</pre></div>
</div>
<p>Where the components are:</p>
<dl class="docutils">
<dt><tt class="docutils literal"><span class="pre">std</span></tt> and <tt class="docutils literal"><span class="pre">dst</span></tt></dt>
<dd>Three or more alphanumerics giving the timezone abbreviations. These will be
propagated into time.tzname</dd>
<dt><tt class="docutils literal"><span class="pre">offset</span></tt></dt>
<dd>The offset has the form: <tt class="docutils literal"><span class="pre">±</span> <span class="pre">hh[:mm[:ss]]</span></tt>. This indicates the value
added the local time to arrive at UTC.  If preceded by a &#8216;-&#8216;, the timezone
is east of the Prime Meridian; otherwise, it is west. If no offset follows
dst, summer time is assumed to be one hour ahead of standard time.</dd>
<dt><tt class="docutils literal"><span class="pre">start[/time],</span> <span class="pre">end[/time]</span></tt></dt>
<dd><p class="first">Indicates when to change to and back from DST. The format of the
start and end dates are one of the following:</p>
<dl class="docutils">
<dt><tt class="samp docutils literal"><span class="pre">J</span><em><span class="pre">n</span></em></tt></dt>
<dd>The Julian day <em>n</em> (1 &lt;= <em>n</em> &lt;= 365). Leap days are not counted, so in
all years February 28 is day 59 and March 1 is day 60.</dd>
<dt><tt class="samp docutils literal"><em><span class="pre">n</span></em></tt></dt>
<dd>The zero-based Julian day (0 &lt;= <em>n</em> &lt;= 365). Leap days are counted, and
it is possible to refer to February 29.</dd>
<dt><tt class="samp docutils literal"><span class="pre">M</span><em><span class="pre">m</span></em><span class="pre">.</span><em><span class="pre">n</span></em><span class="pre">.</span><em><span class="pre">d</span></em></tt></dt>
<dd>The <em>d</em>&#8216;th day (0 &lt;= <em>d</em> &lt;= 6) or week <em>n</em> of month <em>m</em> of the year (1
&lt;= <em>n</em> &lt;= 5, 1 &lt;= <em>m</em> &lt;= 12, where week 5 means &#8220;the last <em>d</em> day in
month <em>m</em>&#8221; which may occur in either the fourth or the fifth
week). Week 1 is the first week in which the <em>d</em>&#8216;th day occurs. Day
zero is Sunday.</dd>
</dl>
<p class="last"><tt class="docutils literal"><span class="pre">time</span></tt> has the same format as <tt class="docutils literal"><span class="pre">offset</span></tt> except that no leading sign
(&#8216;-&#8216; or &#8216;+&#8217;) is allowed. The default, if time is not given, is 02:00:00.</p>
</dd>
</dl>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="p">[</span><span class="s">&#39;TZ&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s">&#39;EST+05EDT,M4.1.0,M10.5.0&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">tzset</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">strftime</span><span class="p">(</span><span class="s">&#39;%X %x %Z&#39;</span><span class="p">)</span>
<span class="go">&#39;02:07:36 05/08/03 EDT&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="p">[</span><span class="s">&#39;TZ&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s">&#39;AEST-10AEDT-11,M10.5.0,M3.5.0&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">tzset</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">strftime</span><span class="p">(</span><span class="s">&#39;%X %x %Z&#39;</span><span class="p">)</span>
<span class="go">&#39;16:08:12 05/08/03 AEST&#39;</span>
</pre></div>
</div>
<p>On many Unix systems (including *BSD, Linux, Solaris, and Darwin), it is more
convenient to use the system&#8217;s zoneinfo (<em class="manpage">tzfile(5)</em>)  database to
specify the timezone rules. To do this, set the  <span class="target" id="index-11"></span><tt class="xref std std-envvar docutils literal"><span class="pre">TZ</span></tt> environment
variable to the path of the required timezone  datafile, relative to the root of
the systems &#8216;zoneinfo&#8217; timezone database, usually located at
<tt class="file docutils literal"><span class="pre">/usr/share/zoneinfo</span></tt>. For example,  <tt class="docutils literal"><span class="pre">'US/Eastern'</span></tt>,
<tt class="docutils literal"><span class="pre">'Australia/Melbourne'</span></tt>, <tt class="docutils literal"><span class="pre">'Egypt'</span></tt> or  <tt class="docutils literal"><span class="pre">'Europe/Amsterdam'</span></tt>.</p>
<div class="highlight-python3"><div class="highlight"><pre><span class="gp">&gt;&gt;&gt; </span><span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="p">[</span><span class="s">&#39;TZ&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s">&#39;US/Eastern&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">tzset</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">tzname</span>
<span class="go">(&#39;EST&#39;, &#39;EDT&#39;)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="p">[</span><span class="s">&#39;TZ&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="s">&#39;Egypt&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">tzset</span><span class="p">()</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">time</span><span class="o">.</span><span class="n">tzname</span>
<span class="go">(&#39;EET&#39;, &#39;EEST&#39;)</span>
</pre></div>
</div>
</dd></dl>

<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<dl class="last docutils">
<dt>Module <a class="reference internal" href="datetime.html#module-datetime" title="datetime: Basic date and time types."><tt class="xref py py-mod docutils literal"><span class="pre">datetime</span></tt></a></dt>
<dd>More object-oriented interface to dates and times.</dd>
<dt>Module <a class="reference internal" href="locale.html#module-locale" title="locale: Internationalization services."><tt class="xref py py-mod docutils literal"><span class="pre">locale</span></tt></a></dt>
<dd>Internationalization services.  The locale setting affects the interpretation
of many format specifiers in <a class="reference internal" href="#time.strftime" title="time.strftime"><tt class="xref py py-func docutils literal"><span class="pre">strftime()</span></tt></a> and <a class="reference internal" href="#time.strptime" title="time.strptime"><tt class="xref py py-func docutils literal"><span class="pre">strptime()</span></tt></a>.</dd>
<dt>Module <a class="reference internal" href="calendar.html#module-calendar" title="calendar: Functions for working with calendars, including some emulation of the Unix cal program."><tt class="xref py py-mod docutils literal"><span class="pre">calendar</span></tt></a></dt>
<dd>General calendar-related functions.   <a class="reference internal" href="calendar.html#calendar.timegm" title="calendar.timegm"><tt class="xref py py-func docutils literal"><span class="pre">timegm()</span></tt></a> is the
inverse of <a class="reference internal" href="#time.gmtime" title="time.gmtime"><tt class="xref py py-func docutils literal"><span class="pre">gmtime()</span></tt></a> from this module.</dd>
</dl>
</div>
<p class="rubric">Footnotes</p>
<table class="docutils footnote" frame="void" id="id2" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>The use of <tt class="docutils literal"><span class="pre">%Z</span></tt> is now deprecated, but the <tt class="docutils literal"><span class="pre">%z</span></tt> escape that expands to the
preferred  hour/minute offset is not supported by all ANSI C libraries. Also, a
strict reading of the original 1982 <span class="target" id="index-12"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc822.html"><strong>RFC 822</strong></a> standard calls for a two-digit
year (%y rather than %Y), but practice moved to 4-digit years long before the
year 2000.  After that, <span class="target" id="index-13"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc822.html"><strong>RFC 822</strong></a> became obsolete and the 4-digit year has
been first recommended by <span class="target" id="index-14"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc1123.html"><strong>RFC 1123</strong></a> and then mandated by <span class="target" id="index-15"></span><a class="rfc reference external" href="http://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a>.</td></tr>
</tbody>
</table>
</div>


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